This is what your brain looks like on LSD

The study revealed several interesting leads. In fMRI scans of subjects’ brains on LSD, researchers found reduced communication between the parahippocampus and regions related to the sense of self such as the retrosplenial cortex. “There’s a kind of dislocation, if you want, in this circuit, and a disintegration in the system which underlies these functions,” explained Carhart-Harris. Most importantly, the magnitude of this observed pattern correlated with subjects’ ratings of the ego-dissolution effect.

In their paper, the researchers compare their overview of results with studies on other psychedelics, such as psilocybin. “It seems increasingly evident that psychedelics reduce the stability and integrity of well-established brain networks and simultaneously reduce the degree of separateness or segregation between them; that is, they induce network disintegration and desegregation,” they write. Carhart-Harris explained this as the brain being less “compartmentalized” and more “unified” under psychedelics, functioning in a “simpler” or “freer” way. In the paper, he and his coauthors characterizes this phenomenon as brain activity becoming more “entropic.”

As for psychedelic visuals, the researchers observed an increase in blood flow in the visual cortex and increased communication between the visual cortex and other areas of the brain when on LSD. “We also saw that the magnitude of this effect correlated with our volunteers’ ratings of complex visual imagery,” Carhart-Harris said.

These findings may seem niche, but they add to a fundamental understanding of how the brain and consciousness works. By showing how LSD acts on the brain, they also bolster research into the therapeutic potential of psychedelic drugs, which has lately seen something of a revival. In their conclusion, the researchers speculate that the “entropic” effects observed under LSD could help to disrupt psychiatric disorders in which the brain has “become entrenched in pathology, such that core behaviors become automated and rigid.”

Perhaps as remarkable as the study’s results, however, is the fact that it was done at all. Since LSD became illegal in 1966, it’s been very difficult to use the drug in scientific research. As a Schedule 1 drug in the UK, LSD is officially considered to have no therapeutic applications, which makes getting the required licences and ethics approvals to run trials with it particularly hard. (Fielding in particular is campaigning for it to be moved to Schedule 2.)

David Nutt, who is well-known for his criticism of UK drug policy, said the study was “easily the most significant thing I’ve ever done.” He noted jovially that his much-publicised dismissal as a government drugs adviser in 2009 allowed him to help follow the vision of psychedelics research Feilding had previously presented.

“I will say to you that this, for human neuroscience, is the same as the discovery of the Higgs boson”

For her part, Feilding characterised the groundbreaking study as a “coming-of-age” of Hoffman’s discovery. “But for the taboo surrounding this field, he would, surely, have won the Nobel Prize,” she said.

She spoke of her own use of LSD after being introduced to it in the 60s, and her enduring aim “to re-integrate these valuable compounds into the fabric of society, and to make their benefits available where appropriate.”

There are of course many unanswered questions remaining, and the researchers are working on other studies with psychedelics, the most imminent being a clinical trial looking at the effects of psilocybin (magic mushrooms) in depressed patients.

It’s worth noting this was a small trial, and only involved participants who had previously used psychedelics, which could impact the results. Carhart-Harris also pointed out that it’s difficult to measure things like ego dissolution, which is highly subjective.